Photographic colloid transfer process



PH QTOGRAFHIC CQLLGH) TRANSFER PRQCESS Walter .ll. Weyerts and Eehn 6C. Barnes, Rochester, NFL- assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed May 20, 1959, Ser. No. 814,378

8 Claims. (Cl. 96-28) bodies the exposure to a subject of a substantially unhardened gelatino-silver halide emulsion layer which may contain a gelatin tanning silver halide developing agent as well as a non-tanning silver halide developing agent. Upon activation of the exposed emulsion with an alkaline solution in the presence of the developing agent or agents, tanning development of the more exposed regions of the emulsion corresponding to the highlights of the subject proceeds although some development of the less exposed regions also takes place to provide-visual density for the transferred image as explained in more detail in US. Patent 2,716,059 above. Thereafter the developed emulsion is pressed into contact With an absorbent receiving sheet such as paper to cause the less exposed regions, and thus the less developed regions, of the emulsion to adhere to the receiving sheet. Subsequently, when the emulsion and receiving sheet are separated a stratum of the less exposed regions of the emulsion remains on the sheet and appears as a positive silver image of the original subject.

As mentioned in the above patents, the solution for activation of the exposed emulsion layer is necessarily alkaline to cause the exposed silver halide emulsion to develop rapidly and to be hardened in the more exposed regions. The mentioned patents recommend for this purpose the use of a sodium carbonate solution containing, among other ingredients, gelatin softening agents such as urea.

We have discovered that while the sodium carbonate solutions are for many purposes satisfactory for use in the process, a far superior alkaline activating solution for the process is one containing as the source of alkalinity a fi-lower alkyl aminoethanol such as B-diethylaminoethanol, fi-monomethylaminoethanol or [idimethylaminoethanol. These alkaline materials have the property of supplying the requisite alkalinity for the process yet can be readily packaged in the form of noncrystallizing concentrated solutions Whereas packages of the sodium carbonate compositions tend to cake and thus dissolve with difficulty. Also the carbonate solutions tend to crystallize out on processing equipment and eventually to render movable parts diflicult or impossible to operate. Furthermore, with many gelatino-silverhalide emulsions used in the process, it is not necessary to add a gelatin softening agent to the activator solution to facilitate transfer of the emulsion image if the mentioned amines are used as the alkaline component. The process can be operated at higher temperature, more uniform quality of prints is obtained, the paper stock of the sensitive element utilized is not adversely affected by the amine-containing solutions and in one particular application of the process to the making of lithographic printing plates, the printing ink takes more readily to the colloid image transferred to United States Patent ()1 snares 1C6 Patented Ju y 19 1962 the lithographic printing plate than when a sodium carbonate activating solution is used.

The B-lower alkylaminoethanols of our invention are valuable in reducing unwanted transfer of background areas from the matrix to the reception layer and increasing the press life of otfset plate images made by this process.

The following examples will serve to illustrate our invention:

EXAMPLE I A substantially unhardened gelatino-silver halide emulsion (having a hardness as defined in the above patents) is prepared as described in US. Patent 2,716,059 above and containing a mixture of tanning and substantially non-tanning silver halide developing agents. The emulsion is coated on a paper support and dried. The resultant sensitive element is then exposed to a two-toned subject (a line or halftone subject) if desired by reflex printing methods and placed in a 5 percent aqueous solution of [i-diethylaminoethanol.

While development in the alkaline solution is proceeding, light should be excluded to the extent required by the particular silver halide present in the emulsion. With daylight working emulsions limited exposure to room lights may be given during the exposure and development steps. Other emulsions may require the use of the usual safelights during the exposure and processing steps. When the proper amount of exposure has been given, gelatin tanning silver halide development occurs principally in the more highly exposed areas of the emulsion and little or no tanning development in the other areas. When development is complete as determined by trial with the particular emulsion and conditions of operation in use, the sensitive element is pressed into contact with an absorbent sheet such as paper by means of a squeegee blade or rollers. Immediately thereafter the sensitive element and receiving sheet are separated leaving a stratum of the less exposed and thus less hardened regions of the emulsion adhered to the receiving sheet. The result is a positive line or half tone silver-containing image aflixed to the sheet. If desired, the transfer operation may be repeated 2. number of times by merely rewetting the sensitive element in the alkaline solution and squeegeeing to a fresh reception sheet.

Useful results are obtained when e-dimethylaminoethanol and [3-monornethylaminoethanol are used in place of the diethyl compound in the above process. Also mixtures of the three amines can be used.

EXAMPLE II Comparison of Carbonate and Amine Activating Solutions The following solutions were prepared:

the pH.

spaasss Solutions A and B were used for activating exposed samples of a projection speed sensitive element prepared as described in Yutzy et al. U.S. Patent 2,596,756 and when development of each sample was complete transfers were made to lithographic paper plates as described in the Clark et a1. U.S. Patent 2,763,553 granted September 18, 1956, to yield silver-containing images on the hydrophilic surface of the plates. Each plate was then inked and printed in a lithographic printing press. It was noted that in this process Solution B caused the paper support of the exposed element to split apart during the transfer of the colloid image to the printing plate, the transferred image was not uniform in density, and the receptivity of the image for the printing ink was poor. Also, Solution B tended to cause the image on the plate to bleed and thus lose definition when activation of the emulsion was carried out at temperatures of the order of 85 F., whereas Solution A did not produce this eifect.

When the two solutions were tested in the same manner over a range of exposure times for the original sensitive element of from 24 to.44 seconds, it was found that Solution A of the invention was satisfactory and the printing .plates obtained thereby printed well; however, the plates made by exposure below 32 seconds and processing with Solution B were of too poor quality to be run on the printing press. When Solution Bwas used it was necessary to operate in subdued light to avoid fogging the sensitive matrix. Solution A produced sufficient desensitization to permit processing and subsequent transfer to the oifset plate surface under ordinary room light conditions.

' Useful results are obtained in the above processes by varying the composition of the amine solutions to suit the needs of the particular emulsion or process under consideration. Thus, a dye such as present in Solutions A and B above, is not essential for use in the process when making the transfers to ordinary paper receiving sheets although it is useful in improving image density. Additional dyes which may be used are Nigrosine (Cl. 865) and Rhodamine B1 (C1. 749).

In transfer to offset plate surfaces in addition to the expected increase in the legibility of the transferred image when dye is used in the activating solution, there is also unexpectedly a considerably heavier transfer of colloid and enhanced ink receptivity in the subsequent printing operation.

With some gelatino-silver halide emulsions it may still be advantageous to add a gelatin softening agent such as urea or acetamide tofacilitate the transfer of the unhardened regions of the emulsion. The amine solutions may be used over a range of pH of about 9 to 11, it being convenient to use acetic acid for the purpose of adjusting EXAMPLE III A buffered concentrated liquid activator solution was prepared by adding 0.65 cc. of glacial acetic acid to 20 grams of B-diethylaminoethanol. Another concentrate was prepared by adding the same amount of glacial acetic acid to fi-dimethylaminoethanol. When the solutions were diluted with water and used in the process of Example I, prints of satisfactory quality were obtained.

Also, no deposit of crystalline material was observed on the processingequipment during the life of these solutions.

The reception sheet for the processes such as illustrated in Example I (not utilizing lithographic printing plates) is advantageously prepared as described in the Chan et a1. U.S. Patent 2,865,745 issued December 23, 1958, comprising a paper sheet on the surface of which is a mixture of an intensifying agent such as thiourea and a development suppressing agent such assodium formaldehyde bisulfite.

EXAMPLE IV A gelatino-silver bromoiodide emulsion was prepared and to 50 cc. of the melted emulsion was added 1 cc. of

a mixture containing 50 grams of a s-diethylaminoethanol-sulfur dioxide addend, 1 gram of 1-phenyl-4,4- dimethyl-S-pyrazolidone and 10 grams of hydroquinone. The emulsion containing the mixture of developing agents was coated on a support and exposed to a line image, then activated for 30 seconds with a solution of one part of B-diethylaminoethanol in 20 parts of water and then rolled into contact with a paper reception sheet. Upon peeling the sensitive element away from the reception sheet, a visible silver image remained. It was found that several more copies could be obtained by repeating the transfer operation with fresh receiving sheets, preferably wetting the sensitive element between each transfer operation.

in a preferred embodiment of the invention, the gelatin tanning and non-tanning developing agents are present in the emulsion. Other useful tanning and non-tanning silver halide developing agents are disclosed in the above patents. However, the process may be carried out using only a gelatin tanning silver halide developing agent in the emulsion or in the amine solution. Useful tanning and non-tanning developing agents are described in the above patents.

What we claim is:

1. A method of photographic reproduction which comprises exposing to a subject a substantially unhardened gelatino-silver halide emulsion layer, said emulsion being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing said exposed emulsion layer with an aqueous alkaline solution of a ,B-lower alkyl-aminoethanol in the presence of a gelatin tanning silver halide developing agent to obtain a hardened gelatin and silver image in the areas of the emulsion layer corresponding to the highlights of the subject, and substantially unhardened gelatin, silver and silver halide in the areas of the emulsion layer corresponding to the shadows of the subject, said development being such as to prevent any substantial tanning of the emulsion layer in said areas corresponding to the shadows of the subject, pressing a .sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only the shadow areas of the emulsion to adhere to the sheet, and separating said sheet and emulsion layer to transfer only a stratum of said shadow areas of the emulsion layer to said sheet.

2. The process of claim 1 wherein the gelatin tanning silver halide developing agent is present in the emulsion layer before exposure.

3. The process of claim 1 wherein the alkaline solu tion contains fl-diethylaminoethanol.

4. A method of photographic reproduction which comprises exposing to a subject a substantially unhardened galatino-silver halide emulsion layer, said emulsion being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing said exposed emulsion layer with an aqueous alkaline solution of a fi-lower alkylaminoethanol in the presence of both a gelatin tanning silver halide developing agent and a substantially non-tanning silver halide developing agent to obtain a hardened gelatin and silver image in the areas of the emulsion layer corresponding to the highlights of the subject, and substantially unhardened gelatin, silver and silver halide in the areas of the emulsion layer corresponding to the shadows of the subject, said development being such as to prevent any substantial tanning of the emulsion layer in said areas corresponding to the shadows of the subject, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only the shadow areas of the emulsion to adhere to the sheet, and separating said sheet and emulsion layer to transfer only a stratum of said shadow areas of the emulsion layer to said sheet.

5. The process of claim 4 wherein the gelatin tanning silver halide developing agent and the substantially nontanning silver halide developing agent are present in the emulsion layer before exposure.

6. The process of claim 4 wherein the alkaline solution contains ,B-diethylaminoethanol.

7. The process of claim 4 wherein the designated sheet having an absorbent surface is a lithographic plate having a hydrophilic surface. 4

8. The process of claim 4 wherein a dye is present in the aqueous alkaline solution.

References Cited in the file of this patent UNITED STATES PATENTS Dundon Sept. 5, 1933 Dearing et a1 Mar. 20, 1945 Yutzy et a1. Aug. 23, 1955 Lake et a1. June 4, 19 57 

1. A METHOD OF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES EXPOSING TO A SUBJECT A SUBSTANTIALLY UNHARDENED GELATINO-SILVER HALIDE EMULSION LAYER, SAID EMULSION BEING NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED, DEVELOPING SAID EXPOSED EMULSION LAYER WITH AN AQUEOUS ALKALINE SOLUTION OF A B-LOWR ALKYLAMINOETHANOL IN THE PRESENCE OF A GELATIN TANNING SILVER HALIDE DEVELOPING AGENT TO OBTAIN A HARDENED GELATIN AND SILVER IMAGE IN THE AREAS OF THE EMULSION LAYER CORRESPONDING TO THE HIGHLIGHTS OF THE SUBJECT, AND SUBSTANTIALLY UNHARDENED GELATIN, SILVER AND SILVER HALIDE IN THE AREAS OF THE EMULSION LAYER CORRESPONDING TO THE SHADOWS OF THE SUBJECT, SAID DEVELOPMENT BEING SUCH AS TO PREVENT ANY SUBSTANTIAL TANNING OF THE EMULSION LAYER IN SAID AREAS CORRESPONDING TO THE SHADOWS OF THE SUBJECT, PRESSING A SHEET HAVING AN ABSORBENT SURFACE AGAINST SAID EMULSION LAYER WHILE SAID EMULSION LAYER IS MOIST TO CAUSE ONLY THE SHADOW AREAS OF THE EMULSION TO ADHERE TO THE SHEET, AND SEPARATING SAID SHEET AND EMULSION LAYER TO TRANSFER ONLY A STREAM OF SAID SHADOW AREAS OF THE EMULSION LAYER TO SAID SHEET. 